Abraham Borbor was one of three doctors in Liberia who had been given ZMapp and were showing signs of recovery.

ZMapp has been credited with helping several patients recover, including two US doctors.

More than 1,400 people have died from Ebola this year in four West African countries – Guinea, Liberia, Nigeria and Sierra Leone.

Dr Borbor “was showing signs of improvement but yesterday (Sunday) he took a turn for the worse,” Liberian Information Minister Lewis Brown told the BBC.

Sierra Leone’s parliament has passed a new law making it a criminal offence to hide Ebola patients

Liberia’s police, army and fire service are being used to enforce the Ebola quarantine in Monrovia

“What this means for the drugs, I don’t know,” the minister added, without giving further details.

It is believed Dr Borbor died in the capital Monrovia. He was the deputy chief medical doctor at the country’s largest hospital.

Liberia has recently imposed a quarantine in parts of Monrovia to try to stop the spread of the virus.

Last Thursday, police fired live rounds and tear gas during protests among residents of the city’s West Point slum.

Liberia has seen the most deaths – more than 570 – in what is now the worst Ebola outbreak in history.

UK isolation case

In a separate development on Monday, a UK volunteer nurse is being treated at a London hospital after contracting Ebola in Sierra Leone – the first confirmed case of a Briton contracting the virus in the current outbreak.

William Pooley worked earlier this year as a volunteer at The Shepherd’s Hospice in Sierra Leone

William Pooley, 29, returned to the UK on Sunday and is being kept in a special isolation unit.

Supplies of Zmapp are thought to have been used up and he is not currently being treated with the drug.

However, officials have not ruled the use of Zmapp or similar treatments.